1. Field of the Invention
The present invention relates to a method for producing a Group III nitride semiconductor light-emitting device, particularly to a method for a Group III nitride semiconductor light-emitting device having a quantum well structure in which a well layer and a barrier layer are deposited.
2. Background Art
The Group III nitride semiconductor light-emitting device has a light-emitting layer which emits light through recombination of electrons and holes. The light-emitting layer has well layers and barrier layers. The bandgap of the barrier layer is larger than that of the well layer. Some semiconductor light-emitting devices have a multiple quantum well structure (MQW structure) formed by repeatedly depositing the well layer and the barrier layer.
The well layer and the barrier layer are the semiconductor layers having different compositions. Generally, the growth temperature is different between the well layer and the barrier layer. Therefore, in formation of the light-emitting layer having the multiple quantum well structure, the semiconductor layer that has already been formed at a low growth temperature may be damaged when forming a semiconductor layer at a high growth temperature. More specifically, the crystallinity of the semiconductor layer grown at a low temperature may be deteriorated by leaving for a specified time in a high temperature environment. For example, the Indium contained in the well layer is partially evaporated, resulting in uneven composition of the well layer.
Therefore, a protective layer may be provided on the semiconductor layer grown at a low temperature. For example, Japanese Patent Application Laid-Open (kokai) No. H11-68159 discloses the technique of forming a capping layer on the well layer after forming the well layer at a low growth temperature (paragraph [0013] and FIG. 2). This capping layer disappears in the process of temperature rise to form a barrier layer at a high growth temperature (paragraph of [0012] and FIG. 2). Thus, the light-emitting layer can be formed without damaging the well layer.
However, after the capping layer disappeared, the well layer is left directly in a high temperature environment. Therefore, the well layer is not flat or the well layer is damaged in some cases. As a result, the crystallinity of the well layer may be deteriorated. In other words, the light emission efficiency of the semiconductor light-emitting device may be lowered.